Archive for the ‘Evolution’ Category

From The New York Times we learn that chipping sparrows love their neighbors, but only if they are weaklings. Male intruders can invade and take over another bird’s territory and strong invaders are usually the winners. Male chipping sparrows will form a neighborhood coalition to defend their territories, but apparently only if the intruder is weaker. And how do they know this? By the intruder’s song. If the intruding sparrow’s trill is weaker, i.e. slower, then that bird is less aggressive. A faster trill indicates a strong invader.

By The Fat Finch

When I first heard this term I had a vision of little birds spewing out of a volcano. But we’re not talking about that kind of eruption.

In the avian world, a bird irruption is a term scientists use to describe unusually large numbers of non-migratory northern birds that move out of their nesting range, typically in North America’s boreal forest. The birds leave the vast, wild expanse of forest, tundra and wetlands that span the width of Canada and Alaska to spend the winter farther south than normal. The irruption occurs because of changes in food supply.

The species that most commonly engage in irruption behavior are northern owls, such as the Great Gray Owl and Snowy Owl and certain grosbeaks including evening grosbeaks. In irruptive years, large numbers of these species may move down into the United States.

This winter there is an irruption of snowy owls coming down into the United States as far down as Kansas and northern Colorado. And this event is causing another kind of eruption—photographers and birders are swarming into these areas to photograph and view these magnificent birds.

Several springs ago a very large number of western tanagers migrated through my area of the world (New Mexico) and stayed for approximately three weeks before heading to their normal summer homes. Was it an irruption? No, it was simply a normal migration of birds who occasionally stay in larger numbers for a longer period of time before moving on. It was a lucky and enjoyable event—I didn’t get much work done because I was staring out the window constantly looking at these gorgeous birds. They also ate 20 lbs of grape jelly off my oriole feeders during those three weeks.

Bird migration is a familiar and predictable seasonal movement of birds. Species that migrate do so every year at approximately the same time, traveling in a predetermined pattern, often to exactly the same destination time after time. Migrations are closely related to the breeding season and the arrival of spring in the breeding range. In contrast, irruptions are unpredictable. It’s all part of the wonderful and amazing world of birds.

This bird may be to coffee what pigs are to truffles. The “Jacu” bird is the name given to a family of birds—the Guans. Found in the forests of Latin America, there are 15 species. It turns out that these birds have quite the “nose” for good coffee. They eat only the very best of coffee beans and because their diet is vegetarian, their poop is not contaminated by animal proteins. Organic coffee growers are paying workers extra to find and extract the beans from the Jacu’s poop. The beans are then cleaned and peeled by hand.

Time to run out and buy a pound? Not so fast. It costs about $24.00 a pound. Maybe we’ll ask Santa for some next year and post our test results on flavor.

From The New York Times

Sometimes the scientists who study animal behavior solve puzzles and other times they uncover new ones. The war between mockingbirds and cowbirds is a case in point.

Cowbirds are brood parasites, meaning they lay their eggs in the nests of other bird species, thus unloading the messy and demanding business of chick-rearing. They also peck holes in the eggs of the host birds, destroying as many as they can.

Mockingbirds are a favorite target of this plan, and it seems to make perfect sense for them to viciously attack cowbirds when they catch them in the nest.

But when Ros Gloag, then a doctoral student at Oxford, and her colleagues in Argentina looked closely at the war between chalk-browed mockingbirds and shiny cowbirds, they found something unexpected, as they reported in the November issue of Animal Behaviour.

They stationed small video cameras near the nests of 40 pairs of chalk-browed mockingbirds. Over two breeding seasons they recorded more than 200 attacks on intruding cowbirds.

They were surprised to find that these attacks, which their videos show to be quite vicious, did not stop the cowbirds from laying eggs. The cowbirds would hunker down and let the much large mockingbirds deliver hammer blows to the head, but in matter of seconds they would lay an egg and flee.

How could such a failed strategy persist in evolution?

The answer, according to Dr. Gloag, now a postdoctoral researcher at Australian National University, was that the attacks did prevent the cowbirds from carrying out the second prong of their plan, destroying the mockingbird eggs already in the nest.

So the mockingbirds managed to save some of their offspring. They still end up raising unwanted baby cowbird guests. But, said Dr. Gloag, once the eggs hatch, the larger mockingbird chicks compete very well with the smaller cowbirds.

From the National Wildlife Federation

From the American Bird Conservancy: top 10 things you can do in your home or yard to help declining migratory birds

The American Bird Conservancy (ABC) often gets asked how people can help birds during this time of year. Toward that end, ABC has identified the top ten things people can do to aid or protect migratory birds in their homes and yards.

1. Keep your cat indoors—this is best for your cat as well as the birds, as indoor cats live an average of three to seven times longer. Even well fed cats kill birds, and bells on cats don’t effectively warn birds of cat strikes. For more information, go to http://www.abcbirds.org/cats.

3. Eliminate pesticides from your yard—even those pesticides that are not directly toxic to birds can pollute waterways and reduce insects that birds rely on for food.

4. Create backyard habitat—if you have a larger yard, create a diverse landscape by planting native grasses, flowers, and shrubs that attract native birds. You will be rewarded by their beauty and song, and will have fewer insect pests as a result.

5. Donate old birdwatching equipment such as binoculars or spotting scopes to local birdwatching groups—they can get them to schools or biologists in other countries who may not have the resources they need.

7. Buy organic food and drink shade-grown coffee—increasing the market for produce grown without the use of pesticides, which can be toxic to birds and other animals, will reduce the use of these hazardous chemicals in the U.S. and overseas. Shade coffee plantations maintain large trees that provide essential habitat for wintering songbirds.

9. Support bird friendly legislation both locally and in the U.S. Congress.

10. Join a bird conservation group—learn more about birds and support important conservation work.

According to ABC, birds need our help now more than ever. In addition to the ongoing threat of loss of habitat that is becoming magnified by global warming, millions of birds are directly killed due to a number of different human-related causes.
Scientists estimate that 300 million to 1 billion birds die each year from collisions with buildings. Up to 50 million die from encounters with communication towers. At least 11 million die from car strikes. Another 1 million may die each day from attacks by cats left outdoors.

Some of these deaths occur year-round but many occur during the peak spring and fall migrations. Some studies suggest that perhaps as many as half of all migrating birds do not make it back to spring and summer grounds, succumbing to various threats on either end of the journey.

“Protecting and helping birds is not only the right thing to do, it is also good for the economy and the future of our environment. Birds are invaluable as controllers of insect pests and as pollinators of crops, and also generate tremendous economic revenues through the pastimes of bird feeding and birdwatching,” says ABC President George Fenwick.

A recent federal government study reports that over 20 percent of the U.S. population – 48 million people – participates in birdwatching. Of that total, about 42 percent (20 million people) actually travel to see birds. Birders spend about $36 billion annually in pursuit of their pastime. The top five birdwatching states by percentage of total population are: Montana (40%); Maine (39%); Vermont (38%); Minnesota (33%); and Iowa (33%).

From The New York Times

Birds are migrating earlier and earlier each year, and scientists have long suspected that climate change is responsible. A new study by researchers at the University of East Anglia in England shows that individual birds migrate like clockwork, but nesting and hatching are happening earlier as a result of warmer temperatures, and this appears to be linked to the advancing of overall migration patterns.

From Science Daily

A first-of-its-kind study by Boise State University researchers shows that the negative effects of roads on wildlife are largely because of traffic noise.

Biologists have known that bird populations decline near roads. But pinpointing noise as a cause has been a problem because past studies of the effects of road noise on wildlife were conducted in the presence of the other confounding effects of roads. These include visual disturbances, collisions and chemical pollution, among others.

“We present the first study to experimentally apply traffic noise to a roadless area at a landscape scale, thus avoiding the other confounding aspects of roads present in past studies,” said Christopher J. W. McClure, post-doctoral research associate in the Department of Biological Sciences.

“Understanding the effects of road noise can help wildlife managers in the selection, conservation and management of habitat for birds,” said Jesse R. Barber, assistant professor of biological sciences and one of McClure’s fellow researchers.

Beside McClure and Barber, researchers in the study include Heidi E. Ware, graduate student; Jay Carlisle, assistant research professor and research director of the Idaho Bird Observatory; and Gregory Kaltenecker, executive director of the Idaho Bird Observatory.

Researchers created a phantom road on a ridge southeast from Lucky Peak, near the Idaho Bird Observatory’s field site. Putting speakers in trees, they played roadway sounds at intervals, alternating four days of noise on with four days off during the autumn migratory period. The researchers conducted daily bird surveys along their phantom road and at a nearby control site.

“We documented more than a one-quarter decline in bird abundance and almost complete avoidance by some species between noise-on and noise-off periods along the phantom road,” Barber said. “There were no such effects at control sites. This suggests that traffic noise is a major driver of the effects of roads on populations of animals.”

When we moved to Gabriola seven years ago, the first bird I saw in the overgrown, untended garden we inherited with our ‘new’ house was a junco. Although it seems amazing to me now, I’d never noticed this bird in the city. With its black hood and unusual metallic chipping ‘song’, I figured it must be very rare indeed. Then I discovered there are about 630 million Dark-eyed Juncos (Junco hyemalis) in North America. So not very rare after all.

In fact, the junco is one of the most abundant backyard birds on the continent. A ‘rock star study organism’, it’s also one of the most thoroughly studied bird species on the planet. For over forty years Ellen Ketterson, a pioneer in the field of animal behavior from the University of Indiana, has been studying juncos. She explains the fascination: the junco “really lets you study it. … They build their nests on the ground, so you can find them. They thrive in captivity, so you can provide them with seeds, or put them in different social configurations. And they’re content. They actually reveal their biology to you.” Ketterson is one of the scientists whose work is described in “The Ordinary Extraordinary Junco”, an 88-minute video series produced by biologists and filmmakers from Indiana University.

Dark-Eyed Junco by Garry Davey

This fascinating free program explores how juncos behave, especially in terms of evolution. Until seeing this series, the word ‘evolution’ conjured up images of dinosaurs to me. But apparently “Evolution doesn’t just happen over huge numbers of generations or millions of years. It can happen to you or me, or any animal, within our own lifetimes. Amazingly, epigenetic changes to our DNA mean that the genes we pass on to our children can differ from the ones we inherited.” (Zoobiquity, Posted on October 28, 2013 by Sharon McInnes, Natterson-Horowitz and Bowers)

One example of such rapid evolutionary change began in the early 1980s when a small flock of junco migrants remained on the campus of the University of California (UCal) instead of returning to the nearby mountains in winter. When scientists began to study the campus birds, they discovered that this urban population was a new isolated breeding population of Oregon Dark-eyed Juncos. The Ordinary Extraordinary Junco tells the fascinating tale. But let me give you a sneak preview.

Essentially, the UCal juncos demonstrated rapid evolution driven by urbanization. In this case, campus life, with its constant barrage of stimuli, changed the very nature of the juncos. They became, for example, more flexible when foraging and nesting, and bolder than their rural counterparts. They explored more food opportunities, allowed humans to get three times closer than rural juncos (in half the time), and sang at a higher frequency in order to be heard in a noisy urban environment. Ultimately, on the bustling campus, with cars and feral cats and construction noise and artificial lighting at all hours, natural selection favored assertive, flexible, bold juncos. Juncos with spunk.

It turned out these more enterprising juncos were also more attentive, involved parents. As the breeding season of the braver urban birds shifted, for example, the males became more interested in parenting (helping to find food for the nestlings) and less aggressive. (Scientists found they had less testosterone at this time.) These ‘brave’ juncos that were also ‘better’ parents were more likely to survive, breed, and pass on their genes. Soon (in evolutionary terms) these new traits became the norm for this newly-evolved isolated population.

I understand behaviour changing in a new environment; that happens all the time – with birds and people. What surprised me is that the birds’ appearance changed so quickly (they had less white in their tails and less black in their heads within thirty years) and that their genetic makeup, their actual DNA, changed. But apparently this kind of rapid evolution is happening with other populations of urban birds around the world now, just as it did with Darwin’s finches in the Galapagos Islands and cichlid fish in Africa.

If I haven’t whet your appetite quite enough to inspire you to drop everything and go watch the 8-video series, check out the trailer at http://www.youtube.com/watch?v=3kvJTMvaKUg. Then, for the whole amazing story, just google The Ordinary Extraordinary Junco. And enjoy!

This article was first published in The Flying Shingle on October 7 2013.PERMALINK

We met a Barn Owl this week. We liked him, but he didn’t care for us. As a matter of fact, when your author walked in to our store where the local animal rescue people had brought it for educational purposes, the owl lowered its head and shook it in the universally recognized shake of disapproval. The rescuers of the owl told me not to take it personally, but I knew better. That owl was rescued after an encounter with a high voltage electrical line which it would not have encountered were it not for humanity’s insatiable desire for electricity. He had no use for me or any other of my fellow Homo sapiens, except possibly for those who rescued him and now care for him.

The rescuers assured us the owl was “toe dusting.” Fairly new to its role as a teacher of humans, the owl was stressed and toe dusting was the physical sign of that stress. Ornithologists hold that Barn Owls lower their heads and shake it over their talons, either as an aggressive signal or as a defensive behavior.

Toe Dusting

I don’t believe it. They do it as a message of disapproval, just like that herbaceous Mountain Goat on the Olympian Peninsula in Washington State a few weeks ago when it gored a man in the leg and then stood over the man until he bled to death. The animals are getting angry with us and who can blame them?

But even if it was threatening me, that owl has the softest eyes of any bird I’ve ever seen up close. Mind you, if I were a field mouse or a vole scuttling across a snow field on a cold, crystalline night and looked up when that owl’s shadow crossed the snow I doubt that I would find anything soft about those eyes. I would see the eyes of a minister of death. And that shadow I would see the instant before my death would be the first clue I had that an owl was anywhere nearby: Owls are about the only land-dwelling animals who never make a sound they don’t intend to make.

But I was in no danger from the owl, and I loved his eyes. They reminded me of Edward Howe Forbush springing to the defense of Barn Owls in his magisterial Birds of Massachusetts and Other New England States. Defending them from unjust persecution, he called them “benefactors to mankind.”

Like Forbush, I may be susceptible to emotional projection and may have mirrored my own consciousness when I looked in those eyes, but I don’t believe that either. Those were the wise eyes of an old soul looking out at me.

Merlin

The rescuers also brought a Merlin with them. Nothing soft about a Merlin’s eyes I can assure you. Falcon eyes put one in mind of Yeats’ horseman,

Like this:

We’re back from a birding/fly-fishing trip and will now finally address The Mockingbird Problem. Northern Mockingbirds – and about twenty percent of other passerine songbirds – are mimics. They steal their songs from their environments. Imagine the smartest student in class unnecessarily cheating on tests by going around the room and copying little bits of every other student’s answers.

That makes no sense. Instead of getting an “A” on the test, the student would get an “F” because her answers would be gibberish. Yet mockingbirds – obviously the star students in avian music class – do precisely that. Rather than develop their own unique songs, they just copy bits and pieces of the songs of other species.

Why?

Wouldn’t it be easier and less costly to invent their own songs and pass those down to their offspring? Less brain power would be required and learning would be simpler. Besides, the mockingbird isn’t fooling any other birds. They all recognize that the mockingbird isn’t one of them.

Nobody knows. We think we know that they sing for the same reasons as other birds: the males are seeking, stimulating, and keeping mates and they are competing with one another for mates and territories. But no one knows why they evolved singing songs of other birds. The same question can be asked about other mimics such as Common Starlings, Marsh Warblers, Australian Lyrebirds, bowerbirds, scrubbirds, and African Robin-chats.

Chihuahan Desert Mockingbird Locale (Otero Mesa)

We’ve learned a lot about Mockingbird song in the last century though. We know, for instance, that both males and females sing, although females sing only in the summer and only when their mate is off their territory. The males sing most in Spring, less in summer, still less in Autumn and hardly at all in winter. Unmated males sing more than mated males and will, in spring, sing all night long. (I’ve camped on the Chihuahuan Desert and listened to one sing all night long. That mockingbird may have been lonely, but he provided me with one of my favorite backpacking memories.) Unmated males sing in all directions, while mated males tend to sing inward toward their own territories.

Darwin's Mockingbirds

The males possess two entirely different repertoires, one for the spring and another for autumn. One had 203 songs in his mind. Somewhere between 90 and 150 seems about average. They continue to learn new songs for as long as they live. Older birds have larger repertoires than younger ones. Males with the most varied songs may get the largest territories. They may also mate earlier. And they sing all the time during breeding season, warbling away while copulating, eating, and foraging.

And probably they sing silently while dreaming. We know that Zebra Finches dream in song; no reason to suspect a bird that devotes as much of its cranial capacity to learning and remembering complex songs wouldn’t also dream in song.